La et al. (2025) Cloud‐Top Entrainment Instability in Marine Stratocumulus Clouds: Observational Evidence From Collocated Microphysical, Turbulence, and Radiation Measurements

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Journal of Geophysical Research Atmospheres
• Year: 2025
• Date: 2025-11-26
• Authors: Inyeob La, Raymond A. Shaw, Holger Siebert, André Ehrlich, Jae Min Yeom, Seong Soo Yum
• DOI: 10.1029/2025jd044582

Research Groups

ACORES campaign participants

Short Summary

This study uses helicopter-borne observations to investigate the mechanisms governing the descent of entrainment-affected parcels in marine stratocumulus clouds (MSC), focusing on the relative roles of cloud-top entrainment instability (CTEI) and longwave radiative cooling (RC). It finds that sufficiently strong CTEI can dominate RC in driving the descent of diluted parcels, clarifying how CTEI, RC, and entrainment interfacial layer (EIL) thickness jointly shape MSC structure.

Objective

• To examine the mechanisms governing the descent of entrainment-affected (diluted) parcels in marine stratocumulus clouds and to clarify the relative roles of cloud-top entrainment instability (CTEI) and longwave radiative cooling (RC).

Study Configuration

• Spatial Scale: Local (vertical profiles within marine stratocumulus clouds, examining variations from cloud top to base).
• Temporal Scale: Snapshot vertical profiles obtained during the ACORES campaign.

Methodology and Data

• Models used: None (observational study).
• Data sources: Helicopter-borne observations from the ACORES campaign, combining high-resolution in situ vertical profiling with co-located remote sensing.

Main Results

• When Cloud-Top Entrainment Instability (CTEI) conditions were strongly met, inhomogeneous mixing (IM) traits appeared near cloud top, transitioning to apparent homogeneous mixing (HM) traits deeper in the cloud layer, accompanied by localized elevations of cloud base. These HM traits are argued to arise from adiabatic warming and evaporation during descent, consistent with enhanced descent of diluted parcels.
• When CTEI was weakly met or not met, IM traits near the top were weaker, HM traits emerged deeper in the cloud, and cloud base elevation was not observed. These differences are explained by RC-driven buoyancy contrasts modulated by turbulence and EIL thickness, leading to weaker descent of diluted parcels.
• The study provides observational evidence that sufficiently strong CTEI can dominate longwave radiative cooling (RC) in driving diluted-parcel descent.

Contributions

• Provides observational evidence clarifying the relative importance of CTEI and RC in driving the descent of entrainment-affected parcels in marine stratocumulus clouds.
• Integrates findings with prior field studies to explain how CTEI, RC, and EIL thickness jointly shape MSC structure.
• Offers guidance for improved representation of marine stratocumulus clouds in weather and climate models.

Funding

Not specified in the abstract.

Citation

@article{La2025CloudTop,
  author = {La, Inyeob and Shaw, Raymond A. and Siebert, Holger and Ehrlich, André and Yeom, Jae Min and Yum, Seong Soo},
  title = {Cloud‐Top Entrainment Instability in Marine Stratocumulus Clouds: Observational Evidence From Collocated Microphysical, Turbulence, and Radiation Measurements},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2025},
  doi = {10.1029/2025jd044582},
  url = {https://doi.org/10.1029/2025jd044582}
}